Semi-closed-air-chamber refrigeration systems, for example, refrigerated warehouses, walk-in coolers and freezers, etc., have a variety of applications, such as food preservation and storage. In this context, “semi-closed” means that the cooled air-chamber (warehouse space, cooler interior, etc.) is not permanently hermetically sealed, but rather periodically or continuously has warm air infiltrating the chamber. For example, refrigerated warehouses have doors that are periodically opened and closed, as do various freezers and coolers, such as grocery freezers and coolers and walk-in freezers and coolers. Some freezers and coolers, especially ones where there is continual in and out traffic have flexible curtains in place of rigid doors.
Most conventional semi-closed-air-chamber refrigeration systems typically have two primary systems for providing chilled air to the refrigerated space. The first system is a closed-cycle mechanical refrigeration system that utilizes a chemical refrigerant, such as a chlorofluorocarbon, anhydrous ammonia and liquefied propane, that is cycled between a condenser and an evaporator. The second system is an air-handler system that circulates air from the chamber being cooled so that it passes through the evaporator before being returned to the chamber. A drawback of these types of systems is that the refrigerants used can be detrimental to the natural environment and/or humans.
Another type of refrigeration system used for semi-closed-air-chamber refrigeration systems is known as a closed-cycle air refrigeration (CCAR) system. The CCAR system typically takes the place of the chemical-refrigerant-based mechanical system described above. In a CCAR system, dry air is circulated in a closed loop between a load exchanger and a cooling system. An air-handling system circulates air from the chamber being cooled so that it passes through the load exchanger before being returned to the chamber. The reason for using a closed-air-cycle is because the air must be dry and it would be very costly to continuously dehumidify the makeup air that would be needed in an open- or semi closed-cycle air system.